Resist composition and patterning process

ABSTRACT

A resist composition comprising a base polymer and a quencher in the form of an ammonium salt compound having an iodized aromatic ring and a tertiary ester structure offers a high sensitivity and minimal LWR or improved CDU, independent of whether it is of positive or negative tone.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2019-012754 filed in Japan on Jan. 29,2019, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a resist composition and a pattern formingprocess.

BACKGROUND ART

To meet the demand for higher integration density and operating speed ofLSIs, the effort to reduce the pattern rule is in rapid progress. Inparticular, the enlargement of the logic memory market to comply withthe wide-spread use of smart phones drives forward the miniaturizationtechnology. As the advanced miniaturization technology, manufacturing ofmicroelectronic devices at the 10-nm node by double patterning of theArF immersion lithography has been implemented in a mass scale.Manufacturing of 7-nm node devices as the next generation by the doublepatterning technology is approaching to the verge of high-volumeapplication. The candidate for 5-nm node devices as the next generationbut one is EUV lithography.

As the pattern feature size is reduced, approaching to the diffractionlimit of light, light contrast lowers. In the case of positive resistfilm, a lowering of light contrast leads to reductions of resolution andfocus margin of hole and trench patterns. For mitigating the influenceof reduced resolution of resist pattern due to a lowering of lightcontrast, an attempt is made to enhance the dissolution contrast ofresist film.

Chemically amplified resist compositions comprising an acid generatorcapable of generating an acid upon exposure to light or EB includechemically amplified positive resist compositions wherein deprotectionreaction takes place under the action of acid and chemically amplifiednegative resist compositions wherein polarity switch or crosslinkingreaction takes place under the action of acid. Quenchers are often addedto these resist compositions for the purpose of controlling thediffusion of the acid to unexposed region to improve the contrast. Theaddition of quenchers is fully effective to this impose. A number ofamine quenchers were proposed as disclosed in Patent Documents 1 to 3.

With respect to the acid labile group used in (meth)acrylate polymersfor the ArF lithography resist material, deprotection reaction takesplace when a photoacid generator capable of generating a sulfonic acidhaving fluorine substituted at α-position (referred to “α-fluorinatedsulfonic acid”) is used, but not when an acid generator capable ofgenerating a sulfonic acid not having fluorine substituted at α-position(referred to “α-non-fluorinated sulfonic acid”) or carboxylic acid isused. If a sulfonium or iodonium salt capable of generating anα-fluorinated sulfonic acid is combined with a sulfonium or iodoniumsalt capable of generating an α-non-fluorinated sulfonic acid, thesulfonium or iodonium salt capable of generating an α-non-fluorinatedsulfonic acid undergoes ion exchange with the α-fluorinated sulfonicacid. Through the ion exchange, the α-fluorinated sulfonic acid thusgenerated by light exposure is converted back to the sulfonium oriodonium salt while the sulfonium or iodonium salt of anα-non-fluorinated sulfonic acid or carboxylic acid functions as aquencher. Patent Document 4 discloses a resist composition comprising asulfonium or iodonium salt capable of generating carboxylic acid as aquencher.

Patent Document 5 discloses a resist composition comprising an iodizedaniline as a quencher. The aniline has a low basicity which isinsufficient to suppress acid diffusion.

Sulfonium and iodonium salt type quenchers are photo-decomposable likephotoacid generators. That is, the amount of quencher in the exposedregion is reduced. Since acid is generated in the exposed region, thereduced amount of quencher leads to a relatively increased concentrationof acid and hence, an improved contrast. However, the acid diffusion inthe exposed region is not suppressed, indicating the difficulty of aciddiffusion control.

Lowering the PEB temperature is effective for suppressing aciddiffusion. However, the dissolution contrast is reduced, invitingdegradations of resolution and LWR. There is the need for a resistcomposition of new concept featuring controlled acid diffusion and ahigh contrast.

CITATION LIST

Patent Document 1: JP-A 2001-194776

Patent Document 2: JP-A 2002-226470

Patent Document 3: JP-A 2002-363148

Patent Document 4: WO 2008/066011

Patent Document 5: JP-A 2018-097356

DISCLOSURE OF INVENTION

For the acid-catalyzed chemically amplified resist, it is desired todevelop a to quencher capable of reducing the LWR of line patterns orimproving the CDU of hole patterns and increasing sensitivity. To thisend, it is necessary to reduce the distance of acid diffusionsignificantly and to increase the contrast at the same time, that is, toimprove ambivalent properties at the same time.

An object of the invention is to provide a resist composition whichexhibits a high sensitivity and a reduced LWR or improved CDU,independent of whether it is of positive tone or negative tone; and apattern forming process using the same.

The inventors have found that using an ammonium salt compound having aniodized aromatic ring and a tertiary ester structure as the quencher, aresist material having a reduced LWR, improved CDU, high contrast,improved resolution, and wide process margin is obtainable.

In one aspect, the invention provides a resist composition comprising abase polymer and a quencher, the quencher containing at least onecompound selected from ammonium salt compounds having the formula (A-1)and ammonium salt compounds having the formula (A-2).

Herein X is a single bond or a C₁-C₂₀ divalent linking group which maycontain an ether bond, carbonyl moiety, ester bond, amide bond, sultonering, lactam ring, carbonate bond, halogen, hydroxyl moiety or carboxylmoiety. R¹ is hydrogen, hydroxyl, an optionally halo-substituted C₁-C₆alkyl group, optionally halo-substituted C₁-C₆ alkoxy group, tooptionally halo-substituted C₂-C₆ acyloxy group, optionallyhalo-substituted C₁-C₄ alkylsulfonyloxy group, fluorine, chlorine,bromine, amino, nitro, cyano, —NR^(1A)—C(═O)—R^(1B), or—NR^(1A)—C(═O)—O—R^(1B), R^(1A) is hydrogen or a C₁-C₆ alkyl group,R^(1B) is a C₁-C₆ alkyl group or C₂-C₈ alkenyl group. R² and R³ are eachindependently a C₁-C₆ alkyl group, R² and R³ may bond together to form aring with the carbon atom to which they are attached. R⁴, R⁵, R⁷ and R⁸are each independently hydrogen, a C₁-C₄ straight or branched alkylgroup, C₂-C₁₂ straight or branched alkoxycarbonyl group, C₆-C₁₅aryloxycarbonyl group, or C₆-C₁₄ aralkyloxycarbonyl group. R⁶ is a C₁-C₆alkyl group, C₂-C₆ alkenyl group, C₂-C₆ alkynyl group, or C₆-C₁₂ arylgroup. R is a C₂-C₁₀ alicyclic group to form a ring with the nitrogenatom. A^(p-) is a carboxylate, fluorine-free sulfonimide, sulfonamide,halogenated phenoxide or halide anion. The subscript m is an integer of1 to 5, n is an integer of 0 to 4, and 1≤m+n≤5, p is 1 or 2, and q is 1or 2.

The resist composition may further comprise an acid generator capable ofgenerating a sulfonic acid, imide acid or methide acid, and/or anorganic solvent.

In a preferred embodiment, the base polymer comprises recurring unitshaving the formula (a1) or recurring units having the formula (a2).

Herein R^(A) is each independently hydrogen or methyl, R¹¹ and R¹² eachare an acid labile group, Y¹ is a single bond, phenylene group,naphthylene group, or C₁-C₁₂ linking group containing at least onemoiety selected from ester bond and lactone ring, and Y² is a singlebond or ester bond.

Typically the resist composition is a chemically amplified positiveresist composition.

In another embodiment, the base polymer is free of an acid labile group.Typically, the resist composition is a chemically amplified negativeresist composition.

The resist composition may further comprise a surfactant.

In a preferred embodiment, the base polymer further comprises recurringunits of at least one type selected from recurring units having theformulae (f1) to (f3).

Herein R^(A) is each independently hydrogen or methyl. Z¹ is a singlebond, phenylene group, —O—Z¹¹—, —C(═O)—O—Z¹¹— or —C(═O)—NH—Z¹¹—, Z¹¹ isa C₁-C₆ alkanediyl group, C₂-C₆ alkenediyl group, or phenylene group,which may contain a carbonyl, ester bond, ether bond or hydroxyl moiety.Z² is a single bond, —Z²¹—C(═O)—O—, —Z²¹—O— or —Z²¹—O—C(═O)—, Z²¹ is aC₁-C₁₂ alkanediyl group which may contain a carbonyl moiety, ester bondor ether bond. Z³ is a single bond, methylene, ethylene, phenylene,fluorinated phenylene, —O—Z³¹—, —C(═O)—O—Z³¹—, or —C(═O)—NH—Z³¹—, Z³¹ isa C₁-C₆ alkanediyl group, C₂-C₆ alkenediyl group, phenylene group,fluorinated phenylene group, or trifluoromethyl-substituted phenylenegroup, which may contain a carbonyl moiety, ester bond, ether bond orhydroxyl moiety. R²¹ to R²⁸ are each independently a C₁-C₂₀ monovalenthydrocarbon group which may contain a heteroatom, any two of R²³, andR²⁵ or any two of R²⁶, R²⁷ and R²⁸ may bond together to form a ring withthe sulfur atom to which they are attached. “A” is hydrogen ortrifluoromethyl. M⁻ is a non-nucleophilic counter ion.

In another aspect, the invention provides a process for forming apattern comprising the steps of applying the resist composition definedherein to form a resist film on a substrate, exposing the resist film tohigh-energy radiation, and developing the exposed resist film in adeveloper.

Typically, the high-energy radiation is ArF excimer laser radiation ofwavelength 193 mu, KrF excimer laser radiation of wavelength 248 mu, EB,or EUV of wavelength 3 to 15 nm.

Advantageous Effects of Invention

The ammonium salt compound having an iodized aromatic ring is fullyabsorptive to EUV due to iodine, has a sensitizing effect, and is quiteeffective for suppressing acid diffusion by virtue of the large atomicweight of iodine. Since the ammonium salt compound also has anacid-decomposable tertiary ester structure, it is decomposed with acidin the exposed region and converted to an ammonium salt compound havinga lower molecular weight. As a result, the acid in the exposed regionbecomes more active and the contrast is improved. There are obtainedadvantages including low diffusion, high contrast, high sensitivity, lowLWR, and improved CDU. Thus a resist composition having a highsensitivity, low LWR and improved CDU is designed.

DESCRIPTION OF EMBODIMENTS

As used herein, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. The notation(C_(n)-C_(m)) means a group containing from n to m carbon atoms pergroup. As used herein, the term “iodized” compound means aniodine-substituted or iodine-containing compound. In chemical formulae,Me stands for methyl, and Ac for acetyl.

The abbreviations and acronyms have the following meaning.

EB: electron beam

EUV: extreme ultraviolet

Mw: weight average molecular weight

Mn: number average molecular weight

Mw/Mn: molecular weight dispersity

GPC: gel permeation chromatography

PEB: post-exposure bake

PAG: photoacid generator

LWR: line width roughness

CDU: critical dimension uniformity

Resist Composition

The resist composition of the invention is defined as comprising a basepolymer and a quencher containing an ammonium salt compound having aniodized aromatic ring and a tertiary ester structure.

Ammonium Salt Compound

The quencher contains an ammonium salt compound having an iodizedaromatic ring and a tertiary ester structure. Specifically the ammoniumsalt compound has the formula (A-1) or (A-2).

In formulae (A-1) and (A-2), X is a single bond or a C₁-C₂₀ divalentlinking group. The divalent linking group may be straight, branched orcyclic. Examples include straight or branched alkanediyl groups such asmethylene, ethylene, propane-1,2-diyl, propane-1,3-diyl,butane-1,2-diyl, butane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl,hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonan-1,9-diyl,decane-1,10-diyl, udecane-1,11-diyl, and dodecane-1,12-diyl; C₃-C₂₀divalent saturated cyclic hydrocarbon groups such as cyclopentanediyl,cyclohexanediyl, norbornanediyl, and adamantanediyl; C₂-C₂₀ divalentunsaturated aliphatic hydrocarbon groups such as vinylene andpropene-1,3-diyl; C₆-C₂₀ divalent aromatic hydrocarbon groups such asphenylene and naphthylene; and mixtures thereof. The divalent linkinggroup may contain an ether bond, carbonyl moiety, ester bond, amidebond, sultone ring, lactam ring, carbonate bond, halogen, hydroxylmoiety or carboxyl moiety.

In formulae (A-1) and (A-2), R¹ is hydrogen, hydroxyl, an optionallyhalo-substituted C₁-C₆ alkyl group, optionally halo-substituted C₁-C₆alkoxy group, optionally halo-substituted C₂-C₆ acyloxy group,optionally halo-substituted C₁-C₄ alkylsulfonyloxy group, fluorine,chlorine, bromine, amino, nitro, cyano, —NR^(1A)—C(═O)—R^(1B), or—NR^(1A)—C(═O)—O—R^(1B), wherein R^(1A) is hydrogen or a C₁-C₆ alkylgroup, and R^(1B) is a C₁-C₆ alkyl group or C₂-C₈ alkenyl group.

The C₁-C₆ alkyl group may be straight, branched or cyclic, and examplesthereof include methyl, ethyl, n-propyl, isopropyl, cyclopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl,cyclopentyl, n-hexyl, and cyclohexyl. Examples of the alkyl moiety inthe C₁-C₆ alkoxy, C₂-C₆ acyloxy or C₁-C₄ alkylsulfonyloxy group are asexemplified above for the alkyl group of 1 to 6, 1 to 5, or 1 to 4carbon atoms.

The C₂-C₈ alkenyl group may be straight, branched or cyclic, andexamples thereof include vinyl, 1-propenyl, 2-propenyl, butenyl, hexenyland cyclohexenyl.

Among others, R¹ is preferably fluorine, chlorine, bromine, hydroxyl,amino, C₁-C₃ alkyl, C₁-C₃ alkoxy, C₂-C₄ acyloxy, —NR^(1A)—C(═O)—R^(1B)or —NR^(1A)—C(═O)—O—R^(1B). When m is 2 or more, a plurality of groupsR¹ may be the same or different.

In formulae (A-1) and (A-2), R² and R³ are each independently a C₁-C₆alkyl group, R² and R³ may bond together to form a ring with the carbonatom to which they are attached. R⁴, R⁵, R⁷ and R⁸ are eachindependently hydrogen, a C₁-C₄ straight or branched alkyl group, C₂-C₁₂straight or branched alkoxycarbonyl group, C₆-C₁₅ aryloxycarbonyl group,or C₆-C₁₄ aralkyloxycarbonyl group. R⁶ is a C₁-C₆ alkyl group, C₂-C₆alkenyl group, C₂-C₆ alkynyl group, or C₆-C₁₂ aryl group.

The C₁-C₆ alkyl and C₂-C₆ alkenyl groups may be straight, branched orcyclic, and examples thereof are as exemplified above. Examples of theC₁-C₄ straight or branched alkyl group include those exemplified abovewhich are straight or branched and have 1 to 4 carbon atoms. The C₂-C₆alkynyl group may be straight, branched or cyclic and examples thereofinclude ethynyl, propynyl, and butynyl. Examples of the C₆-C₁₂ arylgroup include phenyl, tolyl, xylyl, 1-naphthyl and 2-naphthyl.

Examples of the C₂-C₁₂ straight or branched alkoxycarbonyl group includemethoxycarbonyl, ethoxycarbonyl, n-propyloxycarbonyl,isopropyloxycarbonyl, n-butyloxycarbonyl, isobutyloxycarbonyl,sec-butyloxycarbonyl, tert-butyloxycarbonyl, n-pentyloxycarbonyl,sec-pentyloxycarbonyl, tert-pentyloxycarbonyl, neopentyloxycarbonyl,n-hexyloxycarbonyl, n-heptyloxycarbonyl, n-octyloxycarbonyl,2-ethylhexyloxycarbonyl, n-nonyloxycarbonyl, n-decyloxycarbonyl,n-undecyloxycarbonyl, n-dodecyloxycarbonyl, n-tridecyloxycarbonyl,n-pentadecyloxycarbonyl, vinyloxycarbonyl, 1-propenyloxycarbonyl, and2-propenyloxycarbonyl.

Among others, R² and R³ are preferably C₁-C₄ alkyl groups. R⁶ ispreferably a C₁-C₆ alkyl, C₂-C₄ alkenyl, or C₂-C₄ alkynyl group. R⁴, R⁵,R⁷ and R⁸ are preferably hydrogen, C₁-C₄ straight or branched alkylgroups, or C₂-C₆ straight or branched alkoxycarbonyl groups.

In formulae (A-1) and (A-2), R is a C₂-C₁₀ alicyclic group to form aring with the nitrogen atom in the formula. Examples of the ring Rinclude cyclic hydrocarbons such as cyclopropane, cyclopentane,cyclohexane, norbomane and adamantane, in which one carbon atom isreplaced by nitrogen atom.

In formulae (A-1) and (A-2), m is an integer of 1 to 5, n is an integerof 0 to 4, and 1≤m+n≤5, preferably m is an integer of 2 to 4 and n is 0or 1; p is 1 or 2, and q is 1 or 2.

Examples of the cation in the ammonium salt compound having formula(A-1) are shown below, but not limited thereto.

Examples of the cation in the ammonium salt compound having formula(A-2) are shown below, but not limited thereto.

In formulae (A-1) and (A-2), A^(p-) is a carboxylate anion,fluorine-free sulfonimide anion, sulfonamide anion, halogenatedphenoxide anion or halide ion.

Preferably, the carboxylate anion has the formula (Aa-1) or (Aa-2); thefluorine-free sulfonimide anion has the formula (Ab); the sulfonamideanion has the formula (Ac); and the halogenated phenoxide anion has theformula (Ad), all shown below.

In formula (Aa-1), R^(a1) is hydrogen or a C₁-C₃₀ monovalent hydrocarbongroup which may contain a heteroatom. The monovalent hydrocarbon groupmay be straight, branched or cyclic and examples thereof include C₁-C₃₀alkyl groups, C₂-C₃₀ alkenyl groups, to C₂-C₃₀ alkynyl groups, andC₆-C₂₀ aryl groups. In these groups, some hydrogen may be substituted bya moiety containing a heteroatom such as oxygen, sulfur, nitrogen orhalogen, or some carbon may be replaced by a moiety containing aheteroatom such as oxygen, sulfur or nitrogen, so that the group maycontain an ester bond, ether bond, sulfide bond, sulfoxide moiety,carbonate moiety, carbamate moiety, sulfone moiety, amino moiety, amidebond, hydroxyl moiety, thiol moiety, nitro moiety, or halogen atom.

In formula (Aa-2), R^(a2) is a single bond or a C₁-C₃₀ divalenthydrocarbon group which may contain a heteroatom. The divalenthydrocarbon group may be straight, branched or cyclic and examplesthereof include C₁-C₃₀ alkenediyl groups, C₂-C₃₀ alkenediyl groups,C₂-C₃₀ alkynediyl groups, and C₆-C₂₀ arylene groups. In these groups,some hydrogen may be substituted by a moiety containing a heteroatomsuch as oxygen, sulfur, nitrogen or halogen, or some carbon may bereplaced by a moiety containing a heteroatom such as oxygen, sulfur ornitrogen, so that the group may contain an ester bond, ether bond,sulfide bond, sulfoxide moiety, carbonate moiety, carbamate moiety,sulfone moiety, amino moiety, amide bond, hydroxyl moiety, thiol moiety,nitro moiety, or halogen atom.

In formula (Ab), R^(b1) and R^(b2) are each independently a C₁-C₂₀monovalent hydrocarbon group which may contain a hydroxyl moiety, etherbond or ester bond. Also R^(b1) and R^(b2) may bond together to form aring. The monovalent hydrocarbon group may be straight, branched orcyclic and examples thereof include C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀alkynyl, and C₆-C₁₀ aryl groups.

In formula (Ac), R^(c1) is fluorine, or a C₁-C₁₀ fluoroalkyl group orfluorophenyl group, which may contain a hydroxyl moiety, ether bond orester bond. R^(c2) is hydrogen or a C₁-C₁₀ monovalent hydrocarbon groupwhich may contain a hydroxyl moiety, ether bond or ester bond. AlsoR^(c1) and R^(c2) may bond together to form a ring. The monovalenthydrocarbon group may be straight, branched or cyclic and examplesthereof include C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, and C₆-C₁₀aryl groups.

In formula (Ad), R^(d1) is fluorine, trifluoromethyl,1,1,1,3,3,3-hexafluoro-2-propanol, chlorine, bromine or iodine. R^(d2)is hydrogen, hydroxyl, optionally halo-substituted C₁-C₆ alkyl group,optionally halo-substituted C₁-C₆ alkoxy group, optionallyhalo-substituted C₂-C₆ acyloxy group, optionally halo-substituted C₁-C₄alkylsulfonyloxy group, fluorine, chlorine, bromine, amino, nitro,cyano, —NR^(dA)—C(═O)—R^(dB) or —NR^(dA)—C(═O)—O—R^(dB). R^(dA) ishydrogen or a C₁-C₆ alkyl group. R^(dB) is a C₁-C₆ alkyl group or C₂-C₈alkenyl group. The subscript “a” is an integer of 1 to 5, b is aninteger of 0 to 3, meeting 1≤a+b≤5.

Of the groups represented by R^(d2), R^(dA) and R^(dB), the C₁-C₆ alkylmay be straight, branched or cyclic, and examples thereof includemethyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, cyclobutyl, n-pentyl, cyclopentyl, n-hexyl, andcyclohexyl. Examples of the alkyl moiety in the C₁-C₆ alkoxy, C₂-C₆acyloxy or C₁-C₄ alkylsulfonyloxy group are as exemplified above for thealkyl group of 1 to 6, 1 to 5, or 1 to 4 carbon atoms.

The C₂-C₈ alkenyl group represented by R^(dB) may be straight, branchedor cyclic, and examples thereof include vinyl, 1-propenyl, 2-propenyl,butenyl, hexenyl and cyclohexenyl.

Among others, R^(d2) is preferably fluorine, chlorine, bromine,hydroxyl, amino, C₁-C₃ alkyl, C₁-C₃ alkoxy, C₂-C₄ acyloxy,—NR^(dA)—C(═O)—R^(dB) or —NR^(dA)—C(═O)—O—R^(dB).

Examples of the carboxylate anion are shown below, but not limitedthereto.

Examples of the fluorine-free sulfonimide anion are shown below, but notlimited thereto.

Examples of the sulfonamide anion are shown below, but not limitedthereto.

Examples of the halogenated phenoxide anion are shown below, but notlimited thereto.

Exemplary halide ions include fluoride, chloride, bromide and iodideions.

The ammonium salt compound may be synthesized, for example, byneutralization reaction of an amine compound having an iodized aromaticring and tertiary ester structure with a carboxylic acid, fluorine-freesulfonimide, sulfonamide or hydrogen halide.

The neutralization reaction may be carried out in a resist solution.Specifically, an amine compound having an iodized aromatic ring andtertiary ester structure and a carboxylic acid, fluorine-freesulfonamide, sulfonamide or hydrogen halide are added to a resistsolution. In this step, the carboxylic acid, fluorine-free sulfonimide,sulfonamide or hydrogen halide is preferably added in an amount of 0.5to 1.5 moles, more preferably 0.7 to 1.3 moles per mole of the aminecompound.

The inventive ammonium salt compound functions as a quencher having asensitizing effect in a resist composition. While a conventionalquencher functions to control acid diffusion to endow a resist materialwith a lower sensitivity for thereby reducing LWR or CDU, the inventiveammonium salt compound has a very high acid diffusion controlling effectowing to the non-evaporative ammonium salt and iodine having a largeatomic weight, and a sensitizing effect due to the inclusion of aplurality of iodine atoms with substantial EUV absorption, contributingto a high sensitivity.

Since the inventive ammonium salt compound has an acid-decomposabletertiary ester structure, it is decomposed with acid to a lowermolecular weight. As the ammonium salt compound reduces its molecularweight, its acid diffusion ability decreases and its acid reactivityincreases. It occurs in the exposed region that the ammonium saltcompound reduces its molecular weight under the action of acid. An aciddiffusion control ability is retained in the unexposed region whereasacid diffusion is promoted in the exposed region. Thus the difference inreactivity between the exposed region and the unexposed region isexaggerated, leading to an improvement in reaction contrast. It is thuspossible to improve a contrast while suppressing acid diffusion.

U.S. Pat. No. 10,095,109 (JP-A 2018-172640) discloses a methacrylatehaving a tertiary ester structure and an iodized benzene ring. In thepresence of an acid catalyst, it generates iodized isopropenylbenzene,for example. Because of a high boiling point, the iodized benzenecompound does not evaporate, but remains within the resist film duringPEB. Since the iodized benzene compound is not dissolved in the alkalinedeveloper, it can cause defect formation.

In the inventive ammonium salt compound, the direction of ester bondbonding to iodized benzene ring is reverse to the compound of U.S. Pat.No. 10,095,109. As a result of deprotection, the ammonium salt compoundgenerates an iodized benzoic acid, which causes no development defectsbecause it is highly alkaline soluble.

In the resist composition, the ammonium salt compound is preferablypresent in an amount of 0.001 to 50 parts by weight, more preferably0.01 to 40 parts by weight per 100 parts by weight of the base polymer,as viewed from sensitivity and acid diffusion suppressing effect. Theammonium salt compound may be used alone or in admixture.

In the unexposed region or prior to acid decomposition, the ammoniumsalt compound is highly lipophilic and least dissolvable in alkalinedeveloper. After acid decomposition, it releases an ammonium salt havinga low molecular weight and an iodized aromatic carboxylic acid. Thusalkali solubility is increased, and any pattern film thickness loss isrestrained. The ammonium salt compound is thus effective for preventingpattern defects which can form in the exposed region when a highlylipophilic amine quencher is added.

Base Polymer

Where the resist composition is of positive tone, the base polymercomprises recurring units containing an acid labile group, preferablyrecurring units having the formula (a1) or recurring units having theformula (a2). These units are simply referred to as recurring units (a1)and (a2).

In formulae (a1) and (a2), R^(A) is each independently hydrogen ormethyl. R¹¹ and R¹² each are an acid labile group. Y¹ is a single bond,phenylene or naphthylene group, or C₁-C₁₂ linking group containing atleast one moiety selected from ester bond and lactone ring. Y² is asingle bond or ester bond. When the base polymer contains both recurringunits (a1) and (a2), R¹¹ and R¹² may be the same or different.

Examples of the monomer from which the recurring units (a1) are derivedare shown below, but not limited thereto. R^(A) and R¹¹ are as definedabove.

Examples of the monomer from which the recurring units (a2) are derivedare shown below, but not limited thereto. R^(A) and R¹² are as definedabove.

The acid labile groups represented by R¹¹ and R¹² in formulae (a1) and(a2) may be selected from a variety of such groups, for example, thosegroups described in JP-A 2013-80033 (U.S. Pat. No. 8,574,817) and JP-A2013-083821 (U.S. Pat. No. 8,846,303).

Typical of the acid labile group are groups of the following formulae(AL-1) to (AL-3).

In formulae (AL-1) and (AL-2), R^(L1) and R^(L2) are each independentlya C₁-C₄₀ monovalent hydrocarbon group which may contain a heteroatomsuch as oxygen, sulfur, nitrogen or fluorine. The monovalent hydrocarbongroups may be straight, branched or cyclic while C₁-C₄₀ alkyl groups arepreferred, and C₁-C₂₀ alkyl groups are more preferred. In formula(AL-1), c is an integer of 0 to 10, preferably 1 to 5.

In formula (AL-2), R^(L3) and R^(L4) are each independently hydrogen ora C₁-C₂₀ monovalent hydrocarbon group which may contain a heteroatomsuch as oxygen, sulfur, nitrogen or fluorine. The monovalent hydrocarbongroups may be straight, branched or cyclic while C₁-C₂₀ alkyl groups arepreferred. Any two of R^(L2), R^(L3) and R^(L4) may bond together toform a ring, typically alicyclic, with the carbon atom or carbon andoxygen atoms to which they are attached, the ring containing 3 to 20carbon atoms, preferably 4 to 16 carbon atoms.

In formula (AL-3), R^(L5), R^(L6) and R^(L7) are each independently aC₁-C₂₀ monovalent hydrocarbon group which may contain a heteroatom suchas oxygen, sulfur, nitrogen or fluorine. The monovalent hydrocarbongroups may be straight, branched or cyclic while C₁-C₂₀ alkyl groups arepreferred. Any two of R^(L5), R^(L6) and R^(L7) may bond together toform a ring, typically alicyclic, with the carbon atom to which they areattached, the ring containing 3 to 20 carbon atoms, preferably 4 to 16carbon atoms.

The base polymer may further comprise recurring units (b) having aphenolic hydroxyl group as an adhesive group. Examples of suitablemonomers from which recurring units (b) are derived are given below, butnot limited thereto. Herein R^(A) is as defined above.

Further, recurring units (c) having another adhesive group selected fromhydroxyl (other than the foregoing phenolic hydroxyl), lactone ring,ether bond, ester bond, carbonyl, cyano, and carboxyl groups may also beincorporated in the base polymer. Examples of suitable monomers fromwhich recurring units (c) are derived are given below, but not limitedthereto. Herein R^(A) is as defined above.

In another preferred embodiment, the base polymer may further compriserecurring units (d) selected from units derived from indene, benzofuran,benzothiophene, acenaphthylene, chromone, coumarin, and norbornadiene,or derivatives thereof. Suitable monomers are exemplified below.

Furthermore, recurring units (e) may be incorporated in the basepolymer, which are derived from styrene, vinylnaphthalene,vinylanthracene, vinylpyrene, methyleneindene, vinylpyridine, andvinylcarbazole.

In a further embodiment, recurring units (I) derived from an onium salthaving a polymerizable unsaturated bond may be incorporated in the basepolymer. Specifically, the base polymer may comprise recurring units ofat least one type selected from formulae (f1), (f2) and (f3). Theseunits are simply referred to as recurring units (f1), (f2) and (f3),which may be used alone or in combination of two or more types.

In formulae (f1) to (f3), R^(A) is independently hydrogen or methyl. Z¹is a single bond, phenylene group, —O—Z¹¹—, —C(═O)—O—Z¹¹—, or—C(═O)—NH—Z¹¹—, wherein Z¹¹ is a C₁-C₆ alkanediyl group, C₂-C₆alkenediyl group, or phenylene group, which may contain a carbonyl,ester bond, ether bond or hydroxyl moiety. Z² is a single bond,—Z²¹—C(═O)—O—, —Z²¹—O— or —Z²¹—O—C(═O)—, wherein Z²¹ is a C₁-C₁₂alkanediyl group which may contain a carbonyl moiety, ester bond orether bond. “A” is hydrogen or trifluoromethyl. Z³ is a single bond,methylene, ethylene, phenylene, fluorinated phenylene, —O—Z¹¹—,—C(═O)—O—Z³¹—, or —C(═O)—NH—Z³¹—, wherein Z³¹ is a C₁-C₆ alkanediylgroup, C₂-C₆ alkenediyl group, phenylene group, fluorinated phenylenegroup, or trifluoromethyl-substituted phenylene group, which may containa carbonyl moiety, ester bond, ether bond or hydroxyl moiety. Thealkanediyl and alkenediyl groups may be straight, branched or cyclic.

In formulae (f1) to (f3), R²¹ to R²⁸ are each independently a C₁-C₂₀monovalent hydrocarbon group which may contain a heteroatom. Themonovalent hydrocarbon groups may be straight, branched or cyclic, andexamples thereof include C₁-C₁₂ alkyl groups, C₆-C₁₂ aryl groups, andC₇-C₂₀ aralkyl groups. In these groups, some or all of the hydrogenatoms may be substituted by C₁-C₁₀ alkyl groups, halogen,trifluoromethyl, cyano, nitro, hydroxyl, mercapto, C₁-C₁₀ alkoxy groups,C₂-C₁₀ alkoxycarbonyl groups, or C₂-C₁₀ acyloxy groups, and some carbonatom may be replaced by a carbonyl moiety, ether bond or ester bond. Anytwo of R²³, R²⁴ and R²⁵ or any two of R²⁶, R²⁷ and R²⁸ may bond togetherto form a ring with the sulfur atom to which they are attached.

In formula (f1), M⁻ is a non-nucleophilic counter ion. Examples of thenon-nucleophilic counter ion include halide ions such as chloride andbromide ions; fluoroalkylsulfonate ions such as triflate,1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate;arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate;alkylsulfonate ions such as mesylate and butanesulfonate; imide ionssuch as bis(trifluoromethylsulfonyl)imide,bis(perfluoroethylsulfonyl)imide and bis(perfluorobutylsulfonyl)imide;methide ions such as tris(trifluoromethylsulfonyl)methide andtris(perfluoroethylsulfonyl)methide.

Also included are sulfonate ions having fluorine substituted atα-position as represented by the formula (f1-1) and sulfonate ionshaving fluorine substituted at α- and β-positions as represented by theformula (f1-2).

In formula (f1-1), R³¹ is hydrogen, or a C₁-C₂₀ alkyl group, C₂-C₂₀alkenyl group, or C₆-C₂₀ aryl group, which may contain an ether bond,ester bond, carbonyl moiety, lactone ring, or fluorine atom. The alkyland alkenyl groups may be straight, branched or cyclic.

In formula (f1-2), R³² is hydrogen, or a C₁-C₃₀ alkyl group, C₂-C₂₀ acylgroup, C₂-C₂₀ alkenyl group, C₆-C₂₀ aryl group or C₆-C₂₀ aryloxy group,which may contain an ether bond, ester bond, carbonyl moiety or lactonering. The alkyl, acyl and alkenyl groups may be straight, branched orcyclic.

Examples of the monomer from which recurring unit (f1) is derived areshown below, but not limited thereto. R^(A) and M⁻ are as defined above.

Examples of the monomer from which recurring unit (f2) is derived areshown below, but not limited thereto. R^(A) is as defined above.

Examples of the monomer from which recurring unit (f3) is derived areshown below, but not limited thereto. R^(A) is as defined above.

The attachment of an acid generator to the polymer main chain iseffective in restraining acid diffusion, thereby preventing a reductionof resolution due to blur by acid diffusion. Also LWR is improved sincethe acid generator is uniformly distributed. Where a base polymercontaining recurring units (f) is used, the blending of an acidgenerator of addition type may be omitted.

The base polymer for formulating the positive resist compositioncomprises recurring units (a1) or (a2) having an acid labile group asessential component and additional recurring units (b), (c), (d), (e),and (f) as optional components. A fraction of units (a1), (a2), (b),(c), (d), (e), and (f) is: preferably 0≤a1<1.0, 0≤a2<1.0, 0<a1+a2<1.0,0≤b≤0.9, 0≤c≤0.9, 0≤d≤0.8, 0≤e≤0.8, and 0≤f≤0.5; more preferably0≤a1≤0.9, 0≤a2≤0.9, 0.1≤a1+a2≤0.9, 0≤b≤0.8, 0≤c≤0.8, 0≤d≤0.7, 0≤e≤0.7,and 0≤f≤0.4; and even more preferably 0≤a1≤0.8, 0≤a2≤0.8, 0.1≤a1+a2≤0.8,0≤b≤0.75, 0≤c≤0.75, 0≤d≤0.6, 0≤e≤0.6, and 0≤f≤0.3. Notably, f=f1+f2+f3,meaning that unit (f) is at least one of units (f1) to (f3), anda1+a2+b+c+d+e+f=1.0.

For the base polymer for formulating the negative resist composition, anacid labile group is not necessarily essential. The base polymercomprises recurring units (b), and optionally recurring units (c), (d),(e), and/or (f). A fraction of these units is: preferably 0<b≤1.0,0≤c≤0.9, 0≤d≤0.8, 0≤e≤0.8, and 0≤f≤0.5; more preferably 0.2≤b≤1.0,0≤c≤0.8, 0≤d≤0.7, 0≤e≤0.7, and 0≤f≤0.4; and even more preferably0.3≤b≤1.0, 0≤c≤0.75, 0≤d≤0.6, 0≤e≤0.6, and 0≤f≤0.3. Notably, f=f1+f2+f3,meaning that unit (1) is at least one of units (f1) to (f3), andb+c+d+e+f=1.0.

The base polymer may be synthesized by any desired methods, for example,by dissolving one or more monomers selected from the monomerscorresponding to the foregoing recurring units in an organic solvent,adding a radical polymerization initiator thereto, and heating forpolymerization. Examples of the organic solvent which can be used forpolymerization include toluene, benzene, tetrahydrofuran, diethyl ether,and dioxane. Examples of the polymerization initiator used hereininclude 2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide.Preferably, the reaction temperature is 50 to 80° C. and the reactiontime is 2 to 100 hours, more preferably 5 to 20 hours.

Where a monomer having a hydroxyl group is copolymerized, the hydroxylgroup may be replaced by an acetal group susceptible to deprotectionwith acid, typically ethoxyethoxy, prior to polymerization, and thepolymerization be followed by deprotection with weak acid and water.Alternatively, the hydroxyl group may be replaced by an acetyl, formyl,pivaloyl or similar group prior to polymerization, and thepolymerization be followed by alkaline hydrolysis.

When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, analternative method is possible. Specifically, acetoxystyrene oracetoxyvinylnaphthalene is used instead of hydroxystyrene orhydroxyvinylnaphthalene, and after polymerization, the acetoxy group isdeprotected by alkaline hydrolysis, for thereby converting the polymerproduct to hydroxystyrene or hydroxyvinylnaphthalene. For alkalinehydrolysis, a base such as to aqueous ammonia or triethylamine may beused. Preferably the reaction temperature is −20° C. to 100° C., morepreferably 0° C. to 60° C., and the reaction time is 0.2 to 100 hours,more preferably 0.5 to 20 hours.

The base polymer should preferably have a weight average molecularweight (Mw) in the range of 1,000 to 500,000, and more preferably 2,000to 30,000, as measured by GPC versus polystyrene standards usingtetrahydrofuran (THF) solvent. With too low a Mw, the resist compositionmay become less heat resistant. A polymer with too high a Mw may losealkaline solubility and give rise to a footing phenomenon after patternformation.

If a base polymer has a wide molecular weight distribution or dispersity(Mw/Mn), which indicates the presence of lower and higher molecularweight polymer fractions, there is a possibility that foreign matter isleft on the pattern or the pattern profile is degraded. The influencesof Mw and Mw/Mn become stronger as the pattern rule becomes finer.Therefore, the base polymer should preferably have a narrow dispersity(Mw/Mn) of 1.0 to 2.0, especially 1.0 to 1.5, in order to provide aresist composition suitable for micropatterning to a small feature size.

It is understood that a blend of two or more polymers which differ incompositional ratio, Mw or Mw/Mn is acceptable.

Acid Generator

The resist composition may comprise an acid generator capable ofgenerating a strong acid (referred to as acid generator of additiontype, hereinafter). As used herein, the term “strong acid” refers to acompound having a sufficient acidity to induce deprotection reaction ofan acid labile group on the base polymer in the case of a chemicallyamplified positive resist composition, or a compound having a sufficientacidity to induce acid-catalyzed polarity switch reaction orcrosslinking reaction in the case of a chemically amplified negativeresist composition. The inclusion of such an acid generator ensures thatthe ammonium salt compound functions as a quencher and the inventiveresist composition functions as a chemically amplified positive ornegative resist composition.

The acid generator is typically a compound (PAG) capable of generatingan acid upon exposure to actinic ray or radiation. Although the PAG usedherein may be any compound capable of generating an acid upon exposureto high-energy radiation, those compounds capable of generating sulfonicacid, imide acid (imidic acid) or methide acid are preferred. SuitablePAGs include sulfonium salts, iodonium salts, sulfonyldiazomethane,N-sulfonyloxyimide, and oxime-O-sulfonate acid generators. ExemplaryPAGs are described in JP-A 2008-111103, paragraphs [0122]-[0142] (U.S.Pat. No. 7,537,880).

As the PAG used herein, sulfonium salts having the formula (1-1) andiodonium salts having the formula (1-2) are also preferred.

In formulae (1-1) and (1-2), R¹⁰¹, R¹⁰², R¹⁰³, R¹⁰⁴ and R¹⁰⁵ are eachindependently a C₁-C₂₀ monovalent hydrocarbon group which may contain aheteroatom. Any two of R¹⁰¹, R¹⁰² and R¹⁰³ may bond together to form aring with the sulfur atom to which they are attached. The monovalenthydrocarbon group may be straight, branched or cyclic, and examplesthereof include those exemplified above for R²¹ to R²⁸ in formulae (f1)to (f3).

Examples of the cation in the sulfonium salt having formula (1-1) areshown below, but not limited thereto.

Examples of the cation in the iodonium salt having formula (1-2) areshown below, but not limited thereto.

In formulae (1-1) and (1-2), X⁻ is an anion of the following formula(1A), (1B), (1C) or (1D).

In formula (1A), R^(fa) is fluorine or a C₁-C₄₀ monovalent hydrocarbongroup which may contain a heteroatom. The monovalent hydrocarbon groupmay be straight, branched or cyclic, and examples thereof include thoseexemplified later for R¹⁰⁷.

Of the anions of formula (1A), an anion having the formula (1A′) ispreferred.

In formula (1A′), R¹⁰⁶ is hydrogen or trifluoromethyl, preferablytrifluoromethyl.

R¹⁰⁷ is a C₁-C₃₈ monovalent hydrocarbon group which may contain aheteroatom. As the heteroatom, oxygen, nitrogen, sulfur and halogenatoms are preferred, with oxygen being most preferred. Of the monovalenthydrocarbon groups represented by R¹⁰⁷, those groups of 6 to 30 carbonatoms are preferred from the aspect of achieving a high resolution informing patterns of fine feature size. The monovalent hydrocarbon groupsmay be straight, branched or cyclic. Examples thereof include, but arenot limited to, straight or to branched alkyl groups such as methyl,ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,pentyl, neopentyl, hexyl, heptyl, 2-ethylhexyl, nonyl, undecyl,tridecyl, pentadecyl, heptadecyl, eicosanyl, monovalent saturatedalicyclic hydrocarbon groups such as cyclopentyl, cyclohexyl,1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, norbomylmethyl,tricyclodecanyl, tetracyclododecanyl, tetracyclododecanylmethyl, anddicyclohexylmethyl; monovalent unsaturated aliphatic hydrocarbon groupssuch as allyl and 3-cyclohexenyl; aryl groups such as phenyl, 1-naphthyland 2-naphthyl; and aralkyl groups such as benzyl and diphenylmethyl.Examples of the monovalent hydrocarbon group having a heteroatom includetetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl,acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl,2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and3-oxocyclohexyl. In these groups, some hydrogen may be substituted by amoiety containing a heteroatom such as oxygen, sulfur, nitrogen orhalogen, or some carbon may be replaced by a moiety containing aheteroatom such as oxygen, sulfur or nitrogen, so that the group maycontain a hydroxyl, cyano, carbonyl, ether bond, ester bond, sulfonicacid ester bond, carbonate moiety, lactone ring, sultone ring,carboxylic anhydride or haloalkyl moiety.

With respect to the synthesis of the sulfonium salt having an anion offormula (1A′), reference may be made to JP-A 2007-145797, JP-A2008-106045, JP-A 2009-007327, and JP-A 2009-258695. Also useful are thesulfonium salts described in JP-A 2010-215608, JP-A 2012-041320, JP-A2012-106986, and JP-A 2012-153641.

Examples of the anion having formula (1A) are shown below, but notlimited thereto.

In formula (1B), R^(fb1) and R^(fb2) are each independently fluorine ora C₁-C₄₀ monovalent hydrocarbon group which may contain a heteroatom.The monovalent hydrocarbon group may be straight, branched or cyclic,and examples thereof are as exemplified for R¹⁰⁷. Preferably R^(fb1) andR^(fb2) are fluorine or C₁-C₄ straight fluorinated alkyl groups. Also,R^(fb1) and R^(fb2) may bond together to form a ring with the linkage:—CF₂—SO₂—N⁻—SO₂—CF₂— to which they are attached. It is preferred that acombination of R^(fb1) and R^(fb2) be a fluorinated ethylene orfluorinated propylene group.

In formula (1C), R^(fc1), R^(fc2) and R^(fc3) are each independentlyfluorine or a C₁-C₄₀ monovalent hydrocarbon group which may contain aheteroatom. The monovalent hydrocarbon group may be straight, branchedor cyclic, and examples thereof are as exemplified for R¹⁰⁷. PreferablyR^(fc1), R^(fc2) and R^(fc3) are fluorine or C₁-C₄ straight fluorinatedalkyl groups. Also, R^(fc1) and R^(fc2) may bond together to form a ringwith the linkage: —CF₂—SO₂—C⁻—SO₂—CF₂— to which they are attached. It ispreferred that a combination of R^(fc1) and R^(fc2) be a fluorinatedethylene or fluorinated propylene group.

In formula (1D), R^(fd) is a C₁-C₄₀ monovalent hydrocarbon group whichmay contain a heteroatom. The monovalent hydrocarbon group may bestraight, branched or cyclic, and examples thereof are as exemplifiedabove for R¹⁰⁷.

With respect to the synthesis of the sulfonium salt having an anion offormula (1D), reference may be made to JP-A 2010-215608 and JP-A2014-133723.

Examples of the anion having formula (1D) are shown below, but notlimited thereto.

Notably, the compound having the anion of formula (1D) does not havefluorine at the α-position relative to the sulfo group, but twotrifluoromethyl groups at the β-position. For this reason, it has asufficient acidity to sever the acid labile groups in the resistpolymer. Thus the compound is an effective PAG.

Another preferred PAG is a compound having the formula (2).

In formula (2), R²⁰¹ and R²⁰² are each independently a C₁-C₃₀ monovalenthydrocarbon group which may contain a heteroatom. R²⁰³ is a C₁-C₃₀divalent hydrocarbon group which may contain a heteroatom. Any two ofR²⁰¹, R²⁰² and R²⁰³ may bond together to form a ring with the sulfuratom to which they are attached. L^(A) is a single bond, ether bond or aC₁-C₂₀ divalent hydrocarbon group which may contain a heteroatom. X^(A),X^(B), X^(C) and X^(D) are each independently hydrogen, fluorine ortrifluoromethyl, with the proviso that at least one of X^(A), X^(B),X^(C) and X^(D) is fluorine or trifluoromethyl, and k is an integer of 0to 3.

The monovalent hydrocarbon groups may be straight, branched or cyclic.

Examples thereof include, but are not limited to, straight or branchedalkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, n-nonyl,n-decyl, and 2-ethylhexyl; monovalent saturated cyclic hydrocarbongroups such as cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,cyclohexylbutyl, norbornyl, oxanorbornyl,tricyclo[5.2.1.0^(2,6)]decanyl, and adamantyl; and aryl groups such asphenyl, naphthyl and anthracenyl. In these groups, some hydrogen may besubstituted by a moiety containing a heteroatom such as oxygen, sulfur,nitrogen or halogen, or some carbon may be replaced by a moietycontaining a heteroatom such as oxygen, sulfur or nitrogen, so that thegroup may contain a hydroxyl, cyano, carbonyl, ether bond, ester bond,sulfonic acid ester bond, carbonate moiety, lactone ring, sultone ring,carboxylic anhydride or haloalkyl moiety.

The divalent hydrocarbon groups may be straight, branched or cyclic.Examples thereof include straight or branched alkanediyl groups such asmethylene, ethylene, propane-1,3-diyl, butane-1,4-diyl,pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl,nonan-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl,dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl,pentadecane-1,15-diyl, hexadecane-1,16-diyl, and heptadecane-1,17-diyl;divalent saturated cyclic hydrocarbon groups such as cyclopentanediyl,cyclohexanediyl, norbornanediyl and adamantanediyl; and divalentunsaturated cyclic hydrocarbon groups such as phenylene and naphthylene.In these groups, some hydrogen may be substituted by an alkyl moietysuch as methyl, ethyl, propyl, n-butyl or t-butyl; some hydrogen may besubstituted by a moiety containing a heteroatom such as oxygen, sulfur,nitrogen or halogen; or some carbon may be replaced by a moietycontaining a heteroatom such as oxygen, sulfur or nitrogen, so that thegroup may contain a hydroxyl, cyano, carbonyl, ether bond, ester bond,sulfonic acid ester bond, carbonate, lactone ring, sultone ring,carboxylic anhydride or haloalkyl moiety. Of the heteroatoms, oxygen ispreferred.

Of the PAGs having formula (2), those having formula (2′) are preferred.

In formula (2′), L^(A) is as defined above. R^(HF) is hydrogen ortrifluoromethyl, preferably trifluoromethyl. R³⁰¹, R³⁰² and R³⁰³ areeach independently hydrogen or a C₁-C₂₀ monovalent hydrocarbon groupwhich may contain a heteroatom. The monovalent hydrocarbon groups may bestraight, branched or cyclic, and examples thereof are as exemplifiedabove for R¹⁰⁷. The subscripts x and y are each independently an integerof 0 to 5, and z is an integer of 0 to 4.

Examples of the PAG having formula (2) are shown below, but not limitedthereto. Notably, R^(HF) is as defined above.

Of the foregoing PAGs, those having an anion of formula (1A′) or (1D)are especially preferred because of reduced acid diffusion and highsolubility in the resist solvent. Also those having an anion of formula(2′) are especially preferred because of extremely reduced aciddiffusion.

Also a sulfonium or iodonium salt having an iodized or brominatedaromatic ring-containing anion may be used as the PAG. Suitable aresulfonium and iodonium salts having the formulae (3-1) and (3-2).

In formulae (3-1) and (3-2), X^(BI) is iodine or bromine, and may be thesame or to different when s is 2 or more.

L¹ is a single bond, ether bond, ester bond, or a C₁-C₆ alkanediyl groupwhich may contain an ether bond or ester bond. The alkanediyl group maybe straight, branched or cyclic.

R⁴⁰¹ is a hydroxyl group, carboxyl group, fluorine, chlorine, bromine,amino group, or a C₁-C₂₀ alkyl, C₁-C₂₆ alkoxy, C₂-C₁₀ alkoxycarbonyl,C₂-C₂₀ acyloxy or C₁-C₂₀ alkylsulfonyloxy group, which may containfluorine, chlorine, bromine, hydroxyl, amino or C₁-C₁₀ alkoxy moiety, or—NR^(401A)—C(═O)—R^(401B) or —NR^(401A)—C(═O)—O—R^(401B), whereinR^(401A) is hydrogen, or a C₁-C₆ alkyl group which may contain halogen,hydroxy, C₁-C₆ alkoxy, C₂-C₆ acyl or C₂-C₆ acyloxy moiety, R^(401B) is aC₁-C₁₆ alkyl, C₂-C₁₆ alkenyl or C₆-C₁₂ aryl group, which may containhalogen, hydroxy, C₁-C₆ alkoxy, C₂-C₆ acyl or C₂-C₆ acyloxy moiety. Theforegoing alkyl, alkoxy, alkoxycarbonyl, acyloxy, acyl and alkenylgroups may be straight, branched or cyclic. When t is 2 or more, groupsR⁴⁰¹ may be the same or different. Of these, R⁴⁰¹ is preferablyhydroxyl, —NR^(401A)—C(═O)—R^(401B), —NR^(401A)—C(═O)—O—R^(401B),fluorine, chlorine, bromine, methyl or methoxy.

R⁴⁰² is a single bond or a C₁-C₂₀ divalent linking group when r=1, or aC₁-C₂₀ tri- or tetravalent linking group when r=2 or 3, the linkinggroup optionally containing an oxygen, sulfur or nitrogen atom.

Rf¹ to Rf⁴ are each independently hydrogen, fluorine or trifluoromethyl,at least one of Rf¹ to Rf⁴ is fluorine or trifluoromethyl, or Rf¹ andRf², taken together, may form a carbonyl group. Preferably, both Rf³ andRf⁴ are fluorine.

R⁴⁰³, R⁴⁰⁴, R⁴⁰⁵, R⁴⁰⁶ and R⁴⁰⁷ are each independently a C₁-C₂₀monovalent hydrocarbon group which may contain a heteroatom. Any two ofR⁴⁰³, R⁴⁰⁴ and R⁴⁰⁵ may bond together to form a ring with the sulfuratom to which they are attached. The monovalent hydrocarbon group may bestraight, branched or cyclic, and examples thereof include C₁-C₂₀ alkyl,C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl, C₆-C₂₀ aryl, and C₇-C₂₀ aralkyl groups.In these groups, some or all of the hydrogen atoms may be substituted byhydroxyl, carboxyl, halogen, cyano, nitro, mercapto, sultone, sulfone,or sulfonium salt-containing moieties, and some carbon may be replacedby an ether bond, ester bond, carbonyl moiety, amide bond, carbonatemoiety or sulfonic acid ester bond.

In formulae (3-1) and (3-2), r is an integer of 1 to 3, s is an integerof 1 to 5, and t is an integer of 0 to 3, and 1≤s+t≤5. Preferably, s isan integer of 1 to 3, more preferably 2 or 3, and t is an integer of 0to 2.

Examples of the cation in the sulfonium salt having formula (3-1)include those exemplified above as the cation in the sulfonium salthaving formula (1-1). Examples of the cation in the iodonium salt havingformula (3-2) include those exemplified above as the cation in theiodonium salt having formula (1-2).

Examples of the anion in the onium salts having formulae (3-1) and (3-2)are shown below, but not limited thereto. Herein X^(BI) is as definedabove.

When used, the acid generator of addition type is preferably added in anamount of 0.1 to 50 parts, and more preferably 1 to 40 parts by weightper 100 parts by weight of the base polymer. When the base polymer hasrecurring units (f) incorporated therein and/or when the acid generatorof addition type is added, the positive resist composition functions asa chemically amplified positive resist composition.

Organic Solvent

An organic solvent may be added to the resist composition. The organicsolvent used herein is not particularly limited as long as the foregoingand other components are soluble therein. Examples of the organicsolvent are described in JP-A 2008-111103, paragraphs [0144]-[0145](U.S. Pat. No. 7,537,880). Exemplary solvents include ketones such ascyclohexanone, cyclopentanone and methyl-2-n-pentyl ketone; alcoholssuch as 3-methoxybutanol, 3-methyl-3-methoxybutanol,1-methoxy-2-propanol, 1-ethoxy-2-propanol and diacetone alcohol (DAA);ethers such as propylene glycol monomethyl ether (PGME), ethylene glycolmonomethyl ether, propylene glycol monoethyl to ether, ethylene glycolmonoethyl ether, propylene glycol dimethyl ether, and diethylene glycoldimethyl ether; esters such as propylene glycol monomethyl ether acetate(PGMEA), propylene glycol monoethyl ether acetate, ethyl lactate, ethylpyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, andpropylene glycol mono-tert-butyl ether acetate; and lactones such asγ-butyrolactone, which may be used alone or in admixture.

The organic solvent is preferably added in an amount of 100 to 10,000parts, and more preferably 200 to 8,000 parts by weight per 100 parts byweight of the base polymer.

Other Components

With the foregoing components, other components such as a surfactant,dissolution inhibitor, and crosslinker may be blended in any desiredcombination to formulate a chemically amplified positive or negativeresist composition. This positive or negative resist composition has avery high sensitivity in that the dissolution rate in developer of thebase polymer in exposed areas is accelerated by catalytic reaction. Inaddition, the resist film has a high dissolution contrast, resolution,exposure latitude, and process adaptability, and provides a good patternprofile after exposure, and minimal proximity bias because of restrainedacid diffusion. By virtue of these advantages, the composition is fullyuseful in commercial application and suited as a pattern-formingmaterial for the fabrication of VLSIs.

Exemplary surfactants are described in JP-A 2008-111103, paragraphs[0165]-[0166]. Inclusion of a surfactant may improve or control thecoating characteristics of the resist composition. While the surfactantmay be used alone or in admixture, it is preferably added in an amountof 0.0001 to 10 parts by weight per 100 parts by weight of the basepolymer.

In the case of positive resist compositions, inclusion of a dissolutioninhibitor may lead to an increased difference in dissolution ratebetween exposed and unexposed areas and a further improvement inresolution. In the case of negative resist compositions, a negativepattern may be formed by adding a crosslinker to reduce the dissolutionrate of a resist film in exposed area.

The dissolution inhibitor which can be used herein is a compound havingat least two phenolic hydroxyl groups on the molecule, in which anaverage of from 0 to 100 mol % of all the hydrogen atoms on the phenolichydroxyl groups are replaced by acid labile groups or a compound havingat least one carboxyl group on the molecule, in which an average of 50to 100 mol % of all the hydrogen atoms on the carboxyl groups arereplaced by acid labile groups, both the compounds having a molecularweight of 100 to 1,000, and preferably 150 to 800. Typical are bisphenolA, trisphenol, phenolphthalein, cresol novolac, naphthalenecarboxylicacid, adamantanecarboxylic acid, and cholic acid derivatives in whichthe hydrogen atom on the hydroxyl or carboxyl group is replaced by anacid labile group, as described in U.S. Pat. No. 7,771,914 (JP-A2008-122932, paragraphs [0155]-[0178]).

In the positive resist composition, the dissolution inhibitor ispreferably added in an amount of 0 to 50 parts, more preferably 5 to 40parts by weight per 100 parts by weight of the base polymer. Thedissolution inhibitor may be used alone or in admixture.

Suitable crosslinkers which can be used herein include epoxy compounds,melamine compounds, guanamine compounds, glycoluril compounds and ureacompounds having substituted thereon at least one group selected fromamong methylol, alkoxymethyl and acyloxymethyl groups, isocyanatecompounds, azide compounds, and compounds having a double bond such asan alkenyl ether group. These compounds may be used as an additive orintroduced into a polymer side chain as a pendant. Hydroxy-containingcompounds may also be used as the crosslinker. The crosslinker may beused alone or in admixture.

Of the foregoing crosslinkers, examples of the epoxy compound includetris(2,3-epoxypropyl) isocyanurate, trimethylolmethane triglycidylether, trimethylolpropane triglycidyl ether, and triethylolethanetriglycidyl ether. Examples of the melamine compound includehexamethylol melamine, hexamethoxymethyl melamine, hexamethylol melaminecompounds having 1 to 6 methylol groups methoxymethylated and mixturesthereof, hexamethoxyethyl melamine, hexaacyloxymethyl melamine,hexamethylol melamine compounds having 1 to 6 methylol groupsacyloxymethylated and mixtures thereof. Examples of the guanaminecompound include tetramethylol guanamine, tetramethoxymethyl guanamine,tetramethylol guanamine compounds having 1 to 4 methylol groupsmethoxymethylated and mixtures thereof, tetramethoxyethyl guanamine,tetraacyloxyguanamine, tetramethylol guanamine compounds having 1 to 4methylol groups acyloxymethylated and mixtures thereof. Examples of theglycoluril compound include tetramethylol glycoluril,tetramethoxyglycoluril, tetramethoxymethyl glycoluril, tetramethylolglycoluril compounds having 1 to 4 methylol groups methoxymethylated andmixtures thereof, tetramethylol glycoluril compounds having 1 to 4methylol groups acyloxymethylated and mixtures thereof. Examples of theurea compound include tetramethylol urea, tetramethoxymethyl urea,tetramethylol urea compounds having 1 to 4 methylol groupsmethoxymethylated and mixtures thereof, and tetramethoxyethyl urea.

Suitable isocyanate compounds include tolylene diisocyanate,diphenylmethane diisocyanate, hexamethylene diisocyanate and cyclohexanediisocyanate. Suitable azide compounds include1,1′-biphenyl-4,4′-bisazide, 4,4′-methylidenebisazide, and4,4′-oxybisazide. Examples of the alkenyl ether group-containingcompound include ethylene glycol divinyl ether, triethylene glycoldivinyl ether, 1,2-propanediol divinyl ether, 1,4-butanediol divinylether, tetramethylene glycol divinyl ether, neopentyl glycol divinylether, trimethylol propane trivinyl ether, hexanediol divinyl ether,1,4-cyclohexanediol divinyl ether, pentaerythritol trivinyl ether,pentaerythritol tetravinyl ether, sorbitol tetravinyl ether, sorbitolpentavinyl ether, and trimethylol propane trivinyl ether.

In the negative resist composition, the crosslinker is preferably addedin an amount of 0.1 to 50 parts, more preferably 1 to 40 parts by weightper 100 parts by weight of the base polymer.

In the resist composition of the invention, a quencher other than theinventive ammonium salt compound may be blended. The other quencher istypically selected from conventional basic compounds. Conventional basiccompounds include primary, secondary, and tertiary aliphatic amines,mixed amines, aromatic amines, heterocyclic amines, nitrogen-containingcompounds with carboxyl group, nitrogen-containing compounds withsulfonyl group, nitrogen-containing compounds with hydroxyl group,nitrogen-containing compounds with hydroxyphenyl group, alcoholicnitrogen-containing compounds, amide derivatives, imide derivatives, andcarbamate derivatives. Also included are primary, secondary, andtertiary amine compounds, specifically amine compounds having a hydroxylgroup, ether bond, ester bond, lactone ring, cyano group, or sulfonicacid ester bond as described in JP-A 2008-111103, paragraphs[0146]-[0164], and compounds having a carbamate group as described in JP3790649. Addition of a basic compound may be effective for furthersuppressing the diffusion rate of acid in the resist film or correctingthe pattern profile.

Onium salts such as sulfonium salts, iodonium salts and ammonium saltsof sulfonic acids which are not fluorinated at α-position as describedin U.S. Pat. No. 8,795,942 (JP-A 2008-158339) and similar onium salts ofcarboxylic acid may also be used as the other quencher. While anα-fluorinated sulfonic acid, imide acid, and methide acid are necessaryto deprotect the acid labile group of carboxylic acid ester, anα-non-fluorinated sulfonic acid and a carboxylic acid are released bysalt exchange with an α-non-fluorinated onium salt. An α-non-fluorinatedsulfonic acid and a carboxylic acid function as a quencher because theydo not induce deprotection reaction.

Also useful are quenchers of polymer type as described in U.S. Pat. No.7,598,016 (JP-A 2008-239918). The polymeric quencher segregates at theresist surface after coating and thus enhances the rectangularity ofresist pattern. When a protective film is applied as is often the casein the immersion lithography, the polymeric quencher is also effectivefor preventing a film thickness loss of resist pattern or rounding ofpattern top.

The other quencher is preferably added in an amount of 0 to 5 parts,more preferably 0 to 4 parts by weight per 100 parts by weight of thebase polymer. The other quencher may be used alone or in admixture.

To the resist composition, a water repellency improver may also be addedfor improving the water repellency on surface of a resist film as spincoated. The water repellency improver may be used in the topcoatlessimmersion lithography. Suitable water repellency improvers includepolymers having a fluoroalkyl group and polymers having a specificstructure with a 1,1,1,3,3,3-hexafluoro-2-propanol residue and aredescribed in JP-A 2007-297590 and JP-A 2008-111103, for example. Thewater repellency improver to be added to the resist composition shouldbe soluble in the alkaline developer and organic solvent developer. Thewater repellency improver of specific structure with a1,1,1,3,3,3-hexafluoro-2-propanol residue is well soluble in thedeveloper. A polymer having an amino group or amine salt copolymerizedas recurring units may serve as the water repellent additive and iseffective for preventing evaporation of acid during PEB, thus preventingany hole pattern opening failure after development. The water repellencyimprover may be used alone or in admixture. An appropriate amount of thewater repellency improver is 0 to 20 parts, more preferably 0.5 to 10parts by weight per 100 parts by weight of the base polymer.

Also, an acetylene alcohol may be blended in the resist composition.Suitable acetylene alcohols are described in JP-A 2008-122932,paragraphs [0179]-[0182]. An appropriate amount of the acetylene alcoholblended is 0 to 5 parts by weight per 100 parts by weight of the basepolymer.

Pattern Forming Process

The resist composition is used in the fabrication of various integratedcircuits. Pattern formation using the resist composition may beperformed by well-known lithography processes. The process generallyinvolves coating, exposure, and development. If necessary, anyadditional steps may be added.

For example, the positive resist composition is first applied onto asubstrate on which an integrated circuit is to be formed (e.g., Si,SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG, or organic antireflective coating)or a substrate on which a mask circuit is to be formed (e.g., Cr, CrO,CrON, MoSi₂, or SiO₂) by a suitable coating technique such as spincoating, roll coating, flow coating, dipping, spraying or doctorcoating. The coating is prebaked on a hot plate at a temperature of 60to 150° C. for 10 seconds to 30 minutes, preferably at 80 to 120° C. for30 seconds to 20 minutes. The resulting resist film is generally 0.01 to2 μm thick.

The resist film is then exposed to a desired pattern of high-energyradiation such as UV, deep-UV, EB, EUV, x-ray, soft x-ray, excimer laserlight, γ-ray or synchrotron radiation. When UV, deep-UV, EUV, x-ray,soft x-ray, excimer laser light, γ-ray or synchrotron radiation is usedas the high-energy radiation, the resist film is exposed thereto througha mask having a desired pattern in a dose of preferably about 1 to 200mJ/cm², more preferably about 10 to 100 mJ/cm². When EB is used as thehigh-energy radiation, the resist film is exposed thereto through a maskhaving a desired pattern or directly in a dose of preferably about 0.1to 100 μC/cm², more preferably about 0.5 to 50 μC/cm². It is appreciatedthat the inventive resist composition is suited in micropatterning usingKrF excimer laser, ArF excimer laser, EB, EUV, x-ray, soft x-ray, γ-rayor synchrotron radiation, especially in micropatterning using EB or EUV.

After the exposure, the resist film may be baked (PEB) on a hot plate orin an oven at 30 to 150° C. for 10 seconds to 30 minutes, preferably at50 to 120° C. for 30 seconds to 20 minutes.

After the exposure or PEB, in the case of positive resist, the resistfilm is developed in a developer in the form of an aqueous base solutionfor 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes byconventional techniques such as dip, puddle and spray techniques. Atypical developer is a 0.1 to 10 wt %, preferably 2 to 5 wt % aqueoussolution of tetramethylammonium hydroxide (TMAH), tetraethylammonitunhydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), ortetrabutylammonium hydroxide (TBAH). The resist film in the exposed areais dissolved in the developer whereas the resist film in the unexposedarea is not dissolved. In this way, the desired positive pattern isformed on the substrate. Inversely in the case of negative resist, theexposed area of resist film is insolubilized and the unexposed area isdissolved in the developer.

In an alternative embodiment, a negative pattern may be formed viaorganic solvent development using a positive resist compositioncomprising a base polymer having an acid labile group. The developerused herein is preferably selected from among 2-octanone, 2-nonanone,2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone,diisobutyl ketone, methylcyclohexanone, acetophenone,methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate,pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate,butyl formate, isobutyl formate, pentyl formate, isopentyl formate,methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate,methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyllactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate,pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate,benzyl acetate, methyl phenylacetate, benzyl formate, phenylethylformate, methyl 3-phenylpropionate, benzyl propionate, ethylphenylacetate, and 2-phenylethyl acetate, and mixtures thereof.

At the end of development, the resist film is rinsed. As the rinsingliquid, a solvent which is miscible with the developer and does notdissolve the resist film is preferred. Suitable solvents includealcohols of 3 to 10 carbon atoms, ether compounds of 8 to 12 carbonatoms, alkanes, alkenes, and alkynes of 6 to 12 carbon atoms, andaromatic solvents. Specifically, suitable alcohols of 3 to 10 carbonatoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol,2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol,2-pentanol, 3-pentanol, tert-pentyl alcohol, neopentyl alcohol,2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol,cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol,3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol,2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol,3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol,4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol,cyclohexanol, and 1-octanol. Suitable ether compounds of 8 to 12 carbonatoms include di-n-butyl ether, diisobutyl ether, di-sec-butyl ether,di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether,di-tert-pentyl ether, and di-n-hexyl ether. Suitable alkanes of 6 to 12carbon atoms include hexane, heptane, octane, nonan, decane, undecane,to dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane,methylcyclohexane, dimethylcyclohexane, cycloheptene, cyclooctane, andcyclononane. Suitable alkenes of 6 to 12 carbon atoms include hexene,heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene,cycloheptene, and cyclooctene. Suitable alkynes of 6 to 12 carbon atomsinclude hexyne, heptyne, and octyne. Suitable aromatic solvents includetoluene, xylene, ethylbenzene, isopropylbenzene, tert-butylbenzene andmesitylene. The solvents may be used alone or in admixture.

Rinsing is effective for minimizing the risks of resist pattern collapseand defect formation. However, rinsing is not essential. If rinsing isomitted, the amount of solvent used may be reduced.

A hole or trench pattern after development may be shrunk by the thermalflow, RELACS® or DSA process. A hole pattern is shrunk by coating ashrink agent thereto, and baking such that the shrink agent may undergocrosslinking at the resist surface as a result of the acid catalystdiffusing from the resist layer during bake, and the shrink agent mayattach to the sidewall of the hole pattern. The bake is preferably at atemperature of 70 to 180° C., more preferably 80 to 170° C., for a timeof 10 to 300 seconds. The extra shrink agent is stripped and the holepattern is shrunk.

EXAMPLES

Examples of the invention are given below by way of illustration and notby way of limitation. The abbreviation “pbw” is parts by weight.

Quenchers 1 to 33, Amine Compound 1, and Acid Compound 1 used in resistcompositions have the structure shown below.

Synthesis Example

Synthesis of Base Polymers (Polymers 1 to 4)

Base polymers were prepared by combining suitable monomers, effectingcopolymerization reaction thereof in tetrahydrofuran (THF) solvent,pouring the reaction solution into methanol for crystallization,repeatedly washing with hexane, isolation, and drying. The resultingpolymers, designated Polymers 1 to 4, were analyzed for composition by¹H-NMR spectroscopy, and for Mw and Mw/Mn by GPC versus polystyrenestandards using THF solvent.

Examples 1 to 41 and Comparative Examples 1 to 7

Resist compositions were prepared by dissolving various components in asolvent in accordance with the recipe shown in Tables 1 to 3, andfiltering through a filter having a pore size of 0.2 μm. The solventcontained 100 ppm of surfactant Polyfox PF-636 (Omnova Solutions Inc.).The resist compositions of Examples 1 to 31, 33 to 41, and ComparativeExamples 1 to 6 were of positive tone, while the resist compositions ofExample 32 and Comparative Example 7 were of negative tone. In Example27, Amine Compound 1 and Acid Compound 1 were blended in a molar ratioof 1/1.

The components in Tables 1 to 3 are as identified below.

Organic Solvents:

PGMEA (propylene glycol monomethyl ether acetate)

CyH (cyclohexanone)

PGME (propylene glycol monomethyl ether)

DAA (diacetone alcohol)

Acid Generators PAG 1 to PAG 4

Comparative Quenchers 1 to 7

Additional Quenchers 1, 2

EUV Lithography Test

Each of the resist compositions in Tables 1 to 3 was spin coated on asilicon substrate having a 20-nm coating of silicon-containing spin-onhard mask SHB-A940 (Shin-Etsu Chemical Co., Ltd., silicon content 43 wt%) and prebaked on a hotplate at 105° C. for 60 seconds to form a resistfilm of 60 nm thick. Using an EUV scanner NXE3300 (ASML, NA 0.33, a0.9/0.6, quadrupole illumination), the resist film was exposed to EUVthrough a mask bearing a hole pattern at a pitch 46 nm (on-wafer size)and +20% bias. The resist film was baked (PEB) on a hotplate at thetemperature shown in Tables 1 to 3 for 60 seconds and developed in a2.38 wt % TMAH aqueous solution for 30 seconds to form a hole patternhaving a size of 23 nm in Examples 1 to 31, 33 to 41, and ComparativeExamples 1 to 6 or a dot pattern having a size of 23 nm in Example 32and Comparative Example 7.

The resist pattern was evaluated using CD-SEM (CG-5000, HitachiHigh-Technologies Corp.). The exposure dose that provides a hole or dotpattern having a size of 23 nm is reported as sensitivity. The size of50 holes or dots in that dose was measured, from which a size variation(3a) was computed and reported as CDU.

The resist composition is shown in Tables 1 to 3 together with thesensitivity and CDU of EUV lithography.

TABLE 1 Acid PEB Polymer generator Quencher Organic solvent temp.Sensitivity CDU (pbw) (pbw) (pbw) (pbw) (° C.) (mJ/cm²) (nm) Example 1Polymer 1 PAG 1 Quencher 1 PGMEA (400) 100 26 2.6 (100) (30) (4.87) CyH(2,000) PGME (100) 2 Polymer 1 PAG 2 Quencher 2 PGMEA (400) 100 27 2.7(100) (30) (6.37) CyH (2,000) PGME (100) 3 Polymer 1 PAG 2 Quencher 3PGMEA (400) 100 22 2.6 (100) (30) (8.34) CyH (2,000) PGME (100) 4Polymer 1 PAG 2 Quencher 4 PG/AEA (400) 100 23 2.6 (100) (30) (7.40) CyH(2,000) PGME (100) 5 Polymer 1 PAG 2 Quencher 5 PGMEA (400) 100 24 2.7(100) (30) (6.52) CyH (2,000) PGME (100) 6 Polymer 1 PAG 2 Quencher 6PGMEA (400) 100 24 2.4 (100) (30) (10.13) CyH (2,000) PGME (100) 7Polymer 1 PAG 2 Quencher 7 PGMEA (400) 100 23 2.5 (100) (30) (9.30) CyH(2,000) PGME (100) 8 Polymer 1 PAG 2 Quencher 8 PGMEA (400) 100 23 2.4(100) (30) (9.03) M2,000) PGME (100) 9 Polymer 1 PAG 2 Quencher 9 PGMEA(400) 100 24 2.5 (100) (30) (12.07) CyH (2,000) PGME (100) 10 Polymer 1PAG 2 Quencher 10 PGMEA (400) 100 24 2.6 (100) (30) (12.96) CyH (2,000)PGME (100) 11 Polymer 1 PAG 2 Quencher 11 PGMEA (400) 100 25 2.7 (100)(30) (10.96) CyH (2,000) PGME (100) 12 Polymer 1 PAG 2 Quencher 12 PGMEA(400) 100 25 2.6 (100) (30) (10.28) CyH (2,000) PGME (100) 13 Polymer 1PAG 2 Quencher 13 PGMEA (400) 100 25 2.7 (100) (30) (9.86) CyH (2,000)PGME (100) 14 Polymer 1 PAG 2 Quencher 14 PGMEA (400) 100 25 2.6 (100)(30) (11.96) CyH (2,000) PGME (100) 15 Polymer 1 PAG 2 Quencher 15 PGMEA(400) 100 28 2.6 (100) (30) (7.35) CyH (2,000) PGME (100) 16 Polymer 1PAG 2 Quencher 16 PGMEA (400) 100 28 2.6 (100) (30) (7.77) CyH (2,000)PGME (100) 17 Polymer 1 PAG 2 Quencher 17 PGMEA (400) 100 25 2.4 (100)(30) (8.23) CyH (2,000) PGME (100) 18 Polymer 1 PAG 1 Quencher 18 PGMEA(2,000) 100 25 2.7 (100) (30) (8.37) DAA (500) 19 Polymer 1 PAG 1Quencher 19 PGMEA (2,000) 100 25 2.6 (100) (30) (7.72) DAA (500) 20Polymer 1 PAG 1 Quencher 20 PGMEA (2,000) 100 25 2.6 (100) (30) (7.02)DAA (500)

TABLE 2 Acid PEB Polymer generator Quencher Organic solvent temp.Sensitivity CDU (pbw) (pbw) (pbw) (pbw) (° C.) (mJ/cm²) (nm) Example 21Polymer 1 PAG 1 Quencher 21 PGMEA (2,000) 100 25 2.6 (100) (30) (7.53)DAA (500) 22 Polymer 1 PAG 1 Quencher 22 PGMEA (2,000) 100 25 2.6 (100)(30) (9.24) DAA (500) 23 Polymer 1 PAG 1 Quencher 23 PGMEA (2,000) 10025 2.6 (100) (30) (10.00) DAA (500) 24 Polymer 1 PAG 1 Quencher 24 PGMEA(2,000) 100 24 2.7 (100) (30) (9.04) DAA (500) 25 Polymer 1 PAG 1Quencher 25 PGMEA (2,000) 100 25 2.6 (100) (30) (10.16) DAA (500) 26Polymer 1 PAG 1 Quencher 26 PGMEA (2,000) 100 25 2.6 (100) (30) (9.44)DAA (500) 27 Polymer 1 PAG 1 Amine PGMEA (2,000) 100 24 2.6 (100) (30)Compound 1 DAA (500) (6.26) Acid Compound 1 (3.90) 28 Polymer 2 —Quencher 22 PGMEA (2,000) 100 24 2.1 (100) (9.24) DAA (500) 29 Polymer 3— Quencher 22 PGMEA (2,000) 100 25 2.1 (100) (9.24) DAA (500) 30 Polymer3 PAG 3 Quencher 22 PGMEA (2,000) 100 21 2.4 (100) (15) (9.24) DAA (500)31 Polymer 3 PAG 4 Quencher 22 PGMEA (2,000) 100 22 2.3 (100) (15)(9.24) DAA (500) 32 Polymer 4 PAG 1 Quencher 22 PGMEA (2,000) 100 29 2.4(100) (20) (9.24) DAA (500) 33 Polymer 2 — Quencher 27 PGMEA (2,000) 10025 2.3 (100) (14.24) DAA (500) 34 Polymer 2 — Quencher 28 PGMEA (2,000)100 24 2.3 (100) (11.87) DAA (500) 35 Polymer 2 — Quencher 29 PGMEA(2,000) 100 25 2.5 (100) (8.10) DAA (500) 36 Polymer 2 — Quencher 30PGMEA (2,000) 100 25 2.3 (100) (11.30) DAA (500) 37 Polymer 2 — Quencher31 PGMEA (2,000) 100 26 2.3 (100) (9.56) DAA (500) 38 Polymer 2 —Quencher 32 PGMEA (2,000) 100 25 2.3 (100) (10.98) DAA (500) 39 Polymer2 — Quencher 32 PGMEA (2,000) 100 26 2.2 (100) (5.49) DAA (500)Additional Quencher 1 (2.36) 40 Polymer 2 — Quencher 32 PGMEA (2,000)100 23 2.2 (100) (5.49) DAA (500) Additional Quencher 2 (4.46) 41Polymer 2 — Quencher 33 PGMEA (2,000) 100 22 2.3 (100) (5.27) DAA (500)Additional Quencher 2 (4.46)

TABLE 3 Acid PEB Polymer generator Quencher Organic solvent temp.Sensitivity CDU (pbw) (pbw) (pbw) (pbw) (° C.) (mJ/cm²) (nm) Compar- 1Polymer 1 PAG 2 Comparative PGMEA (400) 100 28 3.5 ative (100) (30)Quencher 1 CyH (2,000) Example (1.20) PGME (100) 2 Polymer 1 PAG 2Comparative PGMEA (400) 100 28 3.2 (100) (30) Quencher 2 CyH (2,000)(1.20) PGME (100) 3 Polymer 1 PAG 2 Comparative PGMEA (400) 100 30 2.9(100) (30) Quencher 3 CyH (2,000) (3.20) PGME (100) 4 Polymer 1 PAG 2Comparative PGMEA (400) 100 28 2.8 (100) (30) Quencher 4 CyH (2,000)(3.20) PGME (100) 5 Polymer 1 PAG 2 Comparative PGMEA (400) 100 38 3.0(100) (30) Quencher 5 CyH (2,000) (3.20) PGME (100) 6 Polymer 1 PAG 2Comparative PGMEA (400) 100 30 3.0 (100) (30) Quencher 6 CyH (2,000)(3.20) PGME (100) 7 Polymer 1 PAG 2 Comparative PGMEA (400) 100 30 4.9(100) (30) Quencher 7 CyH (2,000) (3.65) PGME (100)

It is demonstrated in Tables 1 to 3 that resist compositions comprisingammonium salt compounds containing an iodized aromatic ring and atertiary ester structure form patterns having a high sensitivity and areduced value of CDU.

Japanese Patent Application No. 2019-012754 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

The invention claimed is:
 1. A chemically amplified positive resistcomposition comprising a base polymer comprising recurring units havingthe formula (a1) or recurring units having the formula (a2), an acidgenerator and a quencher, the quencher containing at least one compoundselected from ammonium salt compounds having the formula (A-1) andammonium salt compounds having the formula (A-2):

wherein R^(A) is each independently hydrogen or methyl, R¹¹ and R¹² eachare an acid labile group, Y¹ is a single bond, phenylene group,naphthylene group, or C₁-C₁₂ linking group containing at least onemoiety selected from ester bond and lactone ring, and Y² is a singlebond or ester bond,

wherein X is a single bond or a C₁-C₂₀ divalent linking group which maycontain an ether bond, carbonyl moiety, ester bond, amide bond, sultonering, lactam ring, carbonate bond, halogen, hydroxyl moiety or carboxylmoiety, R¹ is hydrogen, hydroxyl, an optionally halo-substituted C₁-C₆alkyl group, optionally halo-substituted C₁-C₆ alkoxy group, optionallyhalo-substituted C₂-C₆ acyloxy group, optionally halo-substituted C₁-C₄alkylsulfonyloxy group, fluorine, chlorine, bromine, amino, nitro,cyano, —NR^(1A)—C(═O)—R^(1B), or —NR^(1A)—C(═O)—O—R^(1B), R^(1A) ishydrogen or a C₁-C₆ alkyl group, R^(1B) is a C₁-C₆ alkyl group or C₂-C₈alkenyl group, R² and R³ are each independently a C₁-C₆ alkyl group, R²and R³ may bond together to form a ring with the carbon atom to whichthey are attached, R⁴, R⁵, R⁷ and R⁸ are each independently hydrogen, aC₁-C₄ straight or branched alkyl group, C₂-C₁₂ straight or branchedalkoxycarbonyl group, C₆-C₁₅ aryloxycarbonyl group, or C₆-C₁₄aralkyloxycarbonyl group, R⁶ is a C₁-C₆ alkyl group, C₂-C₆ alkenylgroup, C₂-C₆ alkynyl group, or C₆-C₁₂ aryl group, R is a C₂-C₁₀alicyclic group to form a ring with the nitrogen atom, A^(p-) is acarboxylate, fluorine-free sulfonimide, sulfonamide, halogenatedphenoxide or halide anion, m is an integer of 1 to 5, n is an integer of0 to 4, and 1≤m+n≤5, p is 1 or 2, and q is 1 or
 2. 2. The resistcomposition of claim 1 wherein the acid generator is capable ofgenerating a sulfonic acid, imide acid or methide acid.
 3. The resistcomposition of claim 1, further comprising an organic solvent.
 4. Theresist composition of claim 1, further comprising a surfactant.
 5. Aprocess for forming a pattern comprising the steps of applying theresist composition of claim 1 to form a resist film on a substrate,exposing the resist film to high-energy radiation, and developing theexposed resist film in a developer.
 6. The process of claim 5 whereinthe high-energy radiation is ArF excimer laser radiation of wavelength193 nm or KrF excimer laser radiation of wavelength 248 nm.
 7. Theprocess of claim 5 wherein the high-energy radiation is EB or EUV ofwavelength 3 to 15 nm.
 8. A chemically amplified negative resistcomposition comprising a base polymer which is free of an acid labilegroup, an acid generator and a quencher, the quencher containing atleast one compound selected from ammonium salt compounds having theformula (A-1) and ammonium salt compounds having the formula (A-2):

wherein X is a single bond or a C₁-C₂₀ divalent linking group which maycontain an ether bond, carbonyl moiety, ester bond, amide bond, sultonering, lactam ring, carbonate bond, halogen, hydroxyl moiety or carboxylmoiety, R¹ is hydrogen, hydroxyl, an optionally halo-substituted C₁-C₆alkyl group, optionally halo-substituted C₁-C₆ alkoxy group, optionallyhalo-substituted C₂-C₆ acyloxy group, optionally halo-substituted C₁-C₄alkylsulfonyloxy group, fluorine, chlorine, bromine, amino, nitro,cyano, —NR^(1A)—C(═O)—R^(1B), or NR^(1A)—C(═O)—O—R^(1B), R^(1A) ishydrogen or a C₁-C₆ alkyl group, R^(1B) is a C₁-C₆ alkyl group or C₂-C₈alkenyl group, R² and R³ are each independently a C₁-C₆ alkyl group, R²and R³ may bond together to form a ring with the carbon atom to whichthey are attached, R⁴, R⁵, R⁷ and R⁸ are each independently hydrogen, aC₁-C₄ straight or branched alkyl group, C₂-C₁₂ straight or branchedalkoxycarbonyl group, C₆-C₁₅ aryloxycarbonyl group, or C₆-C₁₄aralkyloxycarbonyl group, R⁶ is a C₁-C₆ alkyl group, C₂-C₆ alkenylgroup, C₂-C₆ alkynyl group, or C₆-C₁₂ aryl group, R is a C₂-C₁₀alicyclic group to form a ring with the nitrogen atom, A^(p-) is acarboxylate, fluorine-free sulfonimide, sulfonamide, halogenatedphenoxide or halide anion, m is an integer of 1 to 5, n is an integer of0 to 4, and 1≤m+n≤5, p is 1 or 2, and q is 1 or
 2. 9. The chemicallyamplified negative resist composition of claim 8, further comprising acrosslinker.
 10. The chemically amplified negative resist composition ofclaim 8 wherein the base polymer comprises recurring units (b) having aphenolic hydroxyl group as an adhesive group.
 11. A chemically amplifiedpositive resist composition comprising a base polymer comprisingrecurring units having the formula (a1) or recurring units having theformula (a2) and recurring units of at least one type selected fromrecurring units having the formulae (f1) to (f3), and a quencher, thequencher containing at least one compound selected from ammonium saltcompounds having the formula (A-1) and ammonium salt compounds havingthe formula (A-2):

wherein R^(A) is each independently hydrogen or methyl, R¹¹ and R¹² eachare an acid labile group, Y¹ is a single bond, phenylene group,naphthylene group, or C₁-C₁₂ linking group containing at least onemoiety selected from ester bond and lactone ring, and Y² is a singlebond or ester bond,

wherein R^(A) is each independently hydrogen or methyl, Z¹ is a singlebond, phenylene group, —O—Z¹¹—, —C(═O)—O—Z¹¹ or —C(═O)—NH—Z¹¹—, Z¹¹ is aC₁-C₆ alkanediyl group, C₂-C₆ alkenediyl group, or phenylene group,which may contain a carbonyl, ester bond, ether bond or hydroxyl moiety,Z² is a single bond, —Z²¹—C(═O)—O—, —Z²¹—O— or —Z²¹—O—C(═O)—, Z²¹ is aC₁-C₁₂ alkanediyl group which may contain a carbonyl moiety, ester bondor ether bond, Z³ is a single bond, methylene, ethylene, phenylene,fluorinated phenylene, —O—Z³¹—, —C(═O)—O—Z³¹—, or —C(═O)—NH—Z³¹—, Z³¹ isa C₁-C₆ alkanediyl group, C₂-C₆ alkenediyl group, phenylene group,fluorinated phenylene group, or trifluoromethyl-substituted phenylenegroup, which may contain a carbonyl moiety, ester bond, ether bond orhydroxyl moiety, R²¹ to R²⁸ are each independently a C₁-C₂₀ monovalenthydrocarbon group which may contain a heteroatom, any two of R²³, R²⁴and R²⁵ or any two of R²⁶, R²⁷ and R²⁸ may bond together to form a ringwith the sulfur atom to which they are attached, A is hydrogen ortrifluoromethyl, and M⁻is a non-nucleophilic counter ion,

wherein X is a single bond or a C₁-C₂₀ divalent linking group which maycontain an ether bond, carbonyl moiety, ester bond, amide bond, sultonering, lactam ring, carbonate bond, halogen, hydroxyl moiety or carboxylmoiety, R¹ is hydrogen, hydroxyl, an optionally halo-substituted C₁-C₆alkyl group, optionally halo-substituted C₁-C₆ alkoxy group, optionallyhalo-substituted C₂-C₆ acyloxy group, optionally halo-substituted C₁-C₄alkylsulfonyloxy group, fluorine, chlorine, bromine, amino, nitro,cyano, —NR^(1A)—C(═O)—R^(1B), or —NR^(1A)—C(═O)—O—R^(1B), R^(1A) ishydrogen or a C₁-C₆ alkyl group, R^(1B) is a C₁-C₆ alkyl group or C₂-C₈alkenyl group, R² and R³ are each independently a C₁-C₆ alkyl group, R²and R³ may bond together to form a ring with the carbon atom to whichthey are attached, R⁴, R⁵, R⁷ and R⁸ are each independently hydrogen, aC₁-C₄ straight or branched alkyl group, C₂-C₁₂ straight or branchedalkoxycarbonyl group, C₆-C₁₅ aryloxycarbonyl group, or C₆-C₁₄aralkyloxycarbonyl group, R⁶ is a C₁-C₆ alkyl group, C₂-C₆ alkenylgroup, C₂-C₆ alkynyl group, or C₆-C₁₂ aryl group, R is a C₂-C₁₀alicyclic group to form a ring with the nitrogen atom, A^(p-) is acarboxylate, fluorine-free sulfonimide, sulfonamide, halogenatedphenoxide or halide anion, m is an integer of 1 to 5, n is an integer of0 to 4, and 1≤m+n≤5, p is 1 or 2, and q is 1 or 2.